A. Program-Listing Appendix
This application is filed with an appendix containing source-code listings.
B. Field of the Invention
The present invention relates generally to the field of video production, editing, presentation, authoring and viewing, and in particular to a computer-resident facility that permits editing and relational linkage among digitally represented video segments.
C. Description of the Related Art
The types of available media for storing and accessing video images have increased significantly in recent years. Magnetic videotape and other forms of analog electronic storage have largely supplanted the traditional media, which are based on silver-halide representations of miniaturized images. With the reductions in computer cycle time and the cost of memory devices that have recently been achieved, digital storage of still and moving video images is increasingly becoming feasible and may ultimately replace analog-electronic media.
Digitized video offers substantial advantages over both miniaturized-image and analog-electronic storage forms. All miniaturized-image and many analog devices require serial access of desired material, necessitating lengthy forwarding or rewinding operations to retrieve remotely located material. By contrast, the mechanical devices that manipulate digitally stored data, such as magnetic or optical disk assemblies, operate at a higher rate of speed and with greater accuracy than those associated with the earlier video technologies. This is due primarily to the topology of digital devices, which allows virtually any portion thereof to be accessed within a short interval.
Both miniaturized-image and analog media must generally be physically modified in order to accommodate duplication or translocation of material. For example, film editing requires cutting and splicing by using specialized equipment; videotape editing requires analogous permanent alterations to the tape. Transfers of overlapping material to more than one new location require even more effort, because the overlap portions must be copied onto new blank media before being inserted. Digital technology, in contrast, permits rapid and straightforward duplication or translocation of a particular video segment, which can be accomplished with simple memory operations.
The mechanical limitations associated with non-digital video technology place fundamental limitations on the manner in which image information can be presented. Because the final image sequence must reside on a single portion of recording medium, the order in which image information is presented is effectively unalterable. Absent a parallel array of multiple, coordinated playback devices, viewers cannot be offered the opportunity to depart from the linear image sequence as originally defined and recorded, or to selectively invoke related sequences. Non-digital technology thus limits the viewer's ability to interact with and tailor the presentation to suit individual interests, as well as the composer's ability to create relationships among discrete video segments based on content or other criteria.
For example, researchers are currently investigating the possibility of replacing mass media vehicles such as newspapers and magazines, which can offer only static images, with video material organized into related segments through which a viewer can browse. These segments can be related in any number of ways. Accordingly, with material organized according to subject relationships, the user could follow his or her own chosen pathway through the material, viewing subjects of interest in greater depth while bypassing other subjects. Furthermore, it is possible to configure an interactive system that permits the user to orchestrate the relationships among video segments.
Application of digital technology to video composition and editing can also enhance the human interface to such material. The analog or miniaturized-image system typically identifies image segments by words or one or more images selected therefrom. Both forms of identification can be difficult for a viewer to understand without ambiguity. For example, a still image of a sports figure can be interpreted as connoting an image segment relating to the portrayed individual, some facet of his or her style of play, or the sport itself. This ambiguity can often be dispelled with a verbal reference, but unless the subject is amenable to description in a few words, an adequate verbal characterization may be too long for labelling purposes. These identification techniques and their attendant limitations stem largely from the constraints imposed by non-digital image storage and assembly.
Current applications of digital video technology are limited by available data-compression algorithms and storage devices. Typically, only a small amount of material can be stored in digitally compressed, full-motion video format, and this technique finds significant commercial application only in post-production creation of relatively short "special-effect" segments (such as peeling). However, hardware power and capacity continue to increase, and an infrastructure supporting widespread delivery of digital services will accompany installation of fiberoptic trunks (which has already begun). Consequently, while digitized video images are not currently commonplace, this situation will likely change in the near future.
Exploiting the flexibility and speed of digitally stored video requires an approach to composition that emphasizes the capabilities of modern computational equipment. A digital composition system should be capable of designating video segments interactively for storage or immediate playback, organizing multilayered relationships among the specified segments, and displaying to the user an ordered and adequately labelled selection of related segments for viewing or editing.